Seems odd to integrate with a project with a closed source server.
I do believe keybase offers a browser plugin which allows similar function on any site.
It might be easiest to just use the new metadata feature in mastodon profiles. Add your public key there or somesuch
@RussSharek I meant that would be great if Keybase is the one to integrate Mastodon, just like they did with Reddit and Twitter and Hacker News. But I don't know if it is possible.